Some bus supports for high voltage applications are used to support cylindrical and/or tubular bus conductors.
One such known bus support 10 is illustrated in FIGS. 1 and 2. The bus support 10 includes a bus support body 12 mounted to a corona ring 14. The bus support body 12 includes a plurality of mounting apertures 16 for mounting the bus support 10 to an insulator 22. A cylindrical, tubular bus conductor 24 is received in channels defined by the bus support body 12 and/or keepers 18 connected to the bus support body 12.
The corona ring is used to distribute the electric field gradient and lower its maximum values below the corona threshold to help prevent corona discharge. Corona discharge is an ionization of air adjacent to high voltage conductors. It is sometimes visible as a dim blue glow in the air next to high voltage equipment. It is caused by the leakage of current from the conductor into the air, and can represent a significant waste of power in electric power transmission lines and equipment.
The corona ring (also referred to as a grading ring) such as the one shown in FIGS. 1 and 2 is also used to protect the insulator. The corona ring 14 reduces the potential gradient along the insulator, thereby helping to prevent premature electrical breakdown. The corona ring 14 reduces the gradient at the end of the insulator 22, resulting in a more even voltage gradient along the insulator. This allows for a shorter and/or less expensive insulator to be used for a given voltage.
The corona ring 14 is typically formed by bending a hollow tube in a circle and welding the end points to form a torus. The corona ring should be smooth and therefore substantial machining is typically performed including at the weld point. Forming the corona ring can be a costly and time-consuming process.